Static html pages run from file system instead of built-in web-server

Question

I'm running Intellij 13 Ultimate. I'm trying to open a web page I'm working on, and it's opened from the file system:

file:///Users/<username>/dev/index.html

Instead of something like:

http://localhost:<port>/index.html

Thing is, other projects run as expected and I can't figure out what's misconfigured in this specific project.